From 51d7ad03a716086371e9d81a52593ed3787eb3b2 Mon Sep 17 00:00:00 2001
From: David Chen <davidchen9568@gmail.com>
Date: Sun, 15 Apr 2018 19:08:34 +0800
Subject: [PATCH] Fix incorrect behavior when FuelTable is null.

---
 src/QSP/FuelCalculation/FuelData/IFuelTableExtension.cs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/QSP/FuelCalculation/FuelData/IFuelTableExtension.cs b/src/QSP/FuelCalculation/FuelData/IFuelTableExtension.cs
index 911e8d0a..69e53c71 100644
--- a/src/QSP/FuelCalculation/FuelData/IFuelTableExtension.cs
+++ b/src/QSP/FuelCalculation/FuelData/IFuelTableExtension.cs
@@ -2,9 +2,12 @@
 {
     public static class IFuelTableExtension
     {
+        /// <summary>
+        /// Returns null if f is null.
+        /// </summary>
         public static IFuelTable WithBias(this IFuelTable f, double bias)
         {
-            return new Helper(f, bias);
+            return f == null ? null : new Helper(f, bias);
         }
 
         private class Helper : IFuelTable